Validate local_ip for OVS agent is actual ip address

tunnel_sync() writes this value into ovsdb and value is not validated. In
case non-ip value is written into ovsdb row must be deleted manually.

Change-Id: I57eee81e6821eb2cb26b3d07a39bc94b81243570
Closes-bug: #1284684
Merge "Validate local_ip for OVS agent is actual ip address"